With the advancement of digital technologies in electronic devices, demands for an increase in a capacity of a nonvolatile resistance variable element, a reduction in writing electric power, a reduction in write/read-out time, and longer life have been increasing, for storing data such as images. In response to such demands, it is said that there is a limitation on miniaturization of an existing flash memory using a floating gate.
As a first prior art which can possibly meet the above-mentioned demands, there has been proposed a nonvolatile resistance variable element using a perovskite material (e.g., Pr(1-x)CaXMnO3 [PCMO], LaSrMnO3 [LSMO], GdBaCoXOY [GBCO] or the like) (Patent Document 1). In this technique, a predetermined voltage pulse (a wave-shaped voltage having a short duration time) is applied to the perovskite material to increase or decrease its resistance value, and data are made to correspond to the varying resistance value to store the data.
As a second prior art which makes it possible to vary the resistance value with a unipolar voltage pulse, there has also been proposed a nonvolatile resistance variable element which utilizes that the resistance value of a film comprising transition metal oxide (NiO, V2O, ZnO, Nb2O5, TiO2, WO3, or CoO) is varied by applying the voltage pulse to the transition metal oxide film (see Patent Document 2). For the resistance variable element using the transition metal oxide film, a configuration in which cross-point type memory arrays using diodes are formed into a layered structure is realized.
Patent Document 1: U.S. Pat. No. 6,204,139 Specification
Patent Document 2: Japanese Laid-Open Patent Application Publication No. 2004-363604